Feeder unit, feeder module comprising feeder units, and method for discharging a constant mass flow of one or more powders into a receiving container

ABSTRACT

A method for processing pharmaceutical powders, which comprises providing a feeder module including a plurality of feeder units each with a storage hopper, a weighing cell, a conveyer, and a discharge end, connecting the storage hopper to a refilling system with a refilling valve, connecting the refilling valve to a level or weight indicator disposed above the refilling valve, connecting the discharge end to a common receiving container, refilling the storage hopper with a powder intermittently 40 to 80 times per hour, storing data during refilling, transporting powder from the storage hopper with the respective conveyer, and discharging powder from each feeder unit into the common receiving container. During each refilling of the storage hopper, the refilling valve dispenses powder into the storage hopper and, during the step of transporting the powder from the storage hopper, the conveyer is operated according to the data collected during previous refills.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/640,654, filed on Jul. 3, 2017, which application is

-   -   a continuation of U.S. patent application Ser. No. 14/404,972,        filed on Feb. 6, 2015, which application claimed the priority,        under 35 U.S.C. §§ 119, 120, 363, and 371, of International        Application No. PCT/IB2012/052803, filed Jun. 4, 2012, which        designated the United States and was published in English,        the prior applications are herewith incorporated by reference in        their entireties.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable

FIELD OF THE INVENTION

The present invention relates to a feeder unit comprising a storagehopper, a weighing cell, a conveyer, and a discharge end, the storagehopper being adapted to be connected to a refilling system, and thedischarge end to a receiving container, a working space being defined bythe arithmetic product of dead weight of the feeder unit and therefilling interval. The invention furthermore relates to a feeder modulecomprising a plurality of feeder units, and a method for discharging aconstant mass flow of one or more powders into a receiving container.

BACKGROUND OF THE INVENTION

Within the pharmaceutical industry there is an increasing interest inproviding products of a higher quality, and a number of guidelines andregulations have been formulated during recent years to establish properquality measurement, analysis and control.

In addition to improving the processing efficiency and quality there isa general interest in providing processes that are both environmentallysafer and also pose a reduced risk to an operator of the process. Inparticular, in a process to produce for instance tablets from activepharmaceutical ingredients (API) and various excipients in a powderyform may require the operator to wear a protective breathing apparatus,or otherwise personal protective equipment, like gloves or coverall, toprevent excessive exposure to the API and also the excipients. Reductionof the risk of contamination of the surrounding environment as well asexposure of the operator to a pharmaceutical product in a tablettingprocess was addressed in WO03/020499 (Courtoy), wherein a rotary tabletpress was described. However, WO03/020499 does not take fully intoaccount the interest in providing better process control.

Typical manufacturing processes hitherto employed within thepharmaceutical field are of a batch nature. Batch manufacturingprocesses have a number of advantages and provide satisfactory resultswithin many areas. However, due the increasingly widespread applicationof regulated criteria for monitoring and controlling in particularpharmaceutical manufacturing processes, and to the general increase inthe demands to quality by design, the level of quality of monitoring andcontrol attainable by a batch process is often not sufficient, i.e., dueto the fact that settings are fixed. Furthermore, a relatively largebuffer volume is required, entailing undesired back-mixing of thematerial stream. As a consequence, manufacturers' and customers' focusof interest has shifted to continuous processes, in which settings maybe varied and are allowed to change within a design space. In order toachieve more production output with a batch process, bigger equipmentand bigger buffer volumes, with different process settings to attain thesame output, would be required. This is known as the scale-up problem.More output with a continuous process just requires longer running, withthe ability to maintain the same settings. Furthermore, there is anincreased interest for more robust processing equipment and for theability to control more incoming variation, while maintaining tabletquality. Special precautions have to be taken in order to ensuretraceability in a continuous process, just as the requirements toaccuracy and control within the framework of for instance the PAT(Process Analytical Technology) devised by United States Food and DrugAdministration (FDA).

Some examples of continuous processes have been devised in the priorart, for instance in EP 0 275 834 A1, in which two or more ingredientsare fed into the process line at various feed or inlet points, and theingredients are mixed, dried and subsequently compacted in aconventional tabletting machine. The process line includes a firstmixing unit, a drying unit, a sizing unit and a second mixing unit.

Ideally, the output corresponds to the aggregated input of ingredientsat the feed or inlet points, i.e. all of the material is fed to themanufacturing machine in a continuous flow and at a constant rate. Dueto a variety of factors, this is not feasible in practice. First, it isunder any circumstances almost impossible to adjust the output from themixing and drying units to provide a just-in-time supply of material tothe tabletting machine. Second, the continuous production of tablets ofa desired high level of quality requires careful monitoring, controllingand adjustment of process parameters in order to avoid a large rejectionnumber from the tabletting machine. This may lead to accumulation ofmaterial along the process line awaiting adjustment of certain processparameters. In turn, this inevitably necessitates the use ofintermediate buffer vessels in order to store material upstream of thetablet press.

In a more recent document, WO 2010/128359 (GEA Pharma Systems), acontained module being able to operate by a fully continuous process forthe production of tablets is devised. By this design of the tabletproduction module, all units of the tabletting process may be contained,thus reducing the risk of operator exposure and facilitating operationof the tablet press, as all preparations of the material stream fed tothe tablet press are carried out in a contained and controlled manner.The term “contained” is defined by its level of containment according tosuitable measurements, and is defined as at least dust-tight.

Common to the above modules and processes is that one or more mixingunits are utilized. The term “mixing unit” should in this context beunderstood in its broadest terms. Thus, the mixing unit refers to a unitoperation generally capable of mixing or otherwise processing one, twoor more components into a desired form. The mixing unit may thus also becapable of modifying the physical form of dry component(s) processed inthe mixing unit, e.g. a feed stream of powder(s) may be converted to agranulate comprising the component(s). The mixing unit may be agranulator for making a granulate from dry powders, such as a granulatorto which a granulating liquid is added, or a roller compactor. Furtherexamples include a twin screw blender and a twin screw granulator.Furthermore, the mixing unit may include such equipment as a dryer, adry blender, a continuous dry blender or the like.

Dispensing or dosing the component(s) to the mixing unit, or to areceiving container upstream of the mixing unit, most often takes placefrom storage hoppers connected to feeders which in turn supply themixing unit or receiving container with the desired amount of powder(s)or other component(s). Feeding of powders is carried out by means ofscrew conveyors according to one of two main solutions: volumetricfeeding or gravimetric feeding. In volumetric feeding, material held ina hopper is fed into a process at a constant volume per unit of time,whereas in gravimetric feeding, material is fed into a process at aconstant weight per unit of time. The weight is measured by a weighingcell. Gravimetric feeders may operate on the loss-in-weight principle,which provides for more accurate dosing than feeders operating on otherprinciples.

In particular in the processing of pharmaceutical products, accuratedispensing or dosing of the powders involved is vital, andloss-in-weight feeders are traditionally utilized.

One example of prior art concerned with achieving an increased accuracywhen feeding powders is EP 290 999 B1, in which powders are fed fromstorage hoppers to a weighing hopper and further to a mixing orpreparation container.

Many existing loss-in-weight feeders thus function well but are oftenrelatively voluminous and heavy, and require certain conditions withrespect to for instance the installation conditions in the productionarea.

Even with all of the above-mentioned provisions, there is still a needfor increasing the quality and operating conditions.

Thus, a need exists to overcome the problems with the prior art systems,designs, and processes as discussed above.

SUMMARY OF THE INVENTION

On this background, it is an object of the present invention to providea feeder unit, by which the accuracy is improved, while simultaneouslyfulfilling the demands to flexibility and the overall operationalconditions as regards a reduced risk of exposure of the operator.

In a first aspect, this and further objects are met by a feeder unit ofthe kind mentioned in the introduction which is furthermorecharacterized in that the working space (ws) is below 0.2 kgh.

By this design, the feeder unit is able to dispense a very accuratelymeasured amount of material into a receiving container. Relative tofeeder units having a higher dead weight and usually a lower refillinterval, it is possible to obtain a higher accuracy in the measurementbecause of the lower dead weight of the feeder unit. Lossin-weight-feeders known in the art typically weigh up 20-100 kg.Consequently, a higher inaccuracy is present because the loss in weightis so small, typically 0.05-0.1 g, and the weight of the feeder unit isincluded in weight measurement.

In a preferred embodiment, the working space (ws) is below 0.1 kgh. Byreducing the working space even more, an even higher accuracy isobtained. In one development of the preferred embodiment, the deadweight of the feeder unit lies in the range 1 to 8 kg, preferably 1 to 6kg, more preferably 1 to 3 kg. Additionally or alternatively, thestorage hopper may have a predefined volume to define a capacity of thestorage hopper below 10 liters, preferably below 5 liters, mostpreferably below 3 liters. Furthermore, the maximum net weight of powderin the storage hopper may lie in the interval 50 g to 5000 g and theworking space may be below 0.2 kgh, preferably below 0.1 kgh, mostpreferred below 0.05 kgh.

All these factors contribute to reducing the dead weight of the feederunit, and thereby increasing the accuracy of the measurement.

The feeder unit may comprise a refilling valve connected to the storagehopper and a level or weight indicator above the refilling valve forcontrolled predosing of a refill amount. By using a refilling valveinstead of merely loading an unknown amount of powder into the receivingcontainer, it is possible to recreate the same loading conditions eachtime, which makes it possible to collect data on the output of thedischarge end and thereby in further production runs adjust the speed ofthe conveyer accordingly.

In order to increase the accuracy even further, a controller adapted tostore a conveying parameter together with a level or a weight may beprovided.

The weighing cell may be any weighing cell fulfilling the demands toaccuracy on that point and preferably, the weighing cell is with ElectroMagnetic Force Restoration (EMFR).

In order to allow for detachment of parts of each feeding unit relativeto other parts, it is advantageous that the storage hopper, the conveyerand the discharge end of each feeder unit are releasably connected tothe weighing cell.

The powder may in principle be transported or pumped from the storagehopper to the receiving container in any suitable manner. In a preferredembodiment, the conveyer is a twin screw conveyor.

In one development of this preferred embodiment, at least one,preferably both, of the screws of the twin screw conveyor has a variablepitch along its length underneath the storage hopper.

In a further development, at least one, preferably both, of the screwshas a variable diameter along its length underneath the storage hopper.The variable diameter assures that the whole length of at least onescrew, or of both screws, under the hopper is evenly loaded and herebycreating an even transport volume over the section of the hopper.

In one preferred embodiment, the feeder unit comprises a controller forprocessing weight signals and compensate for external forces.

The feeder unit may further comprise a sensor for sensing materialvariations.

With a particular view to obtaining maximum operator security andisolation of the powder from the surroundings, the storage hopper, theconveyer, and the discharge end of the feeder unit are contained andisolated from the weighing cell.

In another aspect, a feeder module comprising a plurality of feederunits is provided, wherein five to eight feeder units are arranged in aspokes-like configuration, each feeder unit extending radially outwardsfrom an imaginary inner circle defined at the discharge end adapted toface the common receiving container to an imaginary outer circle definedby radially opposite end of each feeder unit, the feeder units beingpositioned substantially on radii extending from the imaginary innercircle. Although the feeder unit according to the invention may beutilized independently, it may thus form part of a feeder module whichalso benefits from the greater accuracy obtained.

In a third aspect of the invention, a method for discharging a constantmass flow of one or more powders into a receiving container is provided,said method being suitable for being operated in a feeder unit of thefirst aspect, said method comprising the steps of:

providing a feeder unit with a storage hopper, a weighing cell, aconveyer, and a discharge end, connecting the storage hopper to arefilling system with a refilling valve,

connecting the refilling valve to a level or weight indicator, the levelor weight indicator being above the refilling valve,

connecting the discharge end to a receiving container,

refilling the storage hopper intermittently at predefined intervals,storing data during refilling,

wherein during refilling, the refilling valve dispenses the same amountof powder into the storage hopper, and

the conveyer is operated according to the data collected during previousrefills.

By connecting a refilling valve instead of merely loading an unknownamount of powder into the receiving container, it is possible torecreate the same loading conditions each time, which makes it possibleto collect data on the output of the discharge end and thereby infurther production runs adjust the speed of the conveyer accordingly. Bystoring data during refilling, by ensuring that during refilling, therefilling valve dispenses the same amount of powder into the storagehopper, and by operating the conveyer according to the data collectedduring previous refills, a substantial increase of the accuracy isobtained, as any effects of refilling are reduced or eliminated.

With the foregoing and other objects in view, there is provided, amethod for processing pharmaceutical powders which comprises the stepsof providing a feeder module including a plurality of feeder units,providing each feeder unit with a storage hopper, a weighing cell, aconveyer, and a discharge end, connecting the storage hopper of eachfeeder unit to a refilling system with a refilling valve, connecting therefilling valve to at least one of a level or weight indicator disposedabove the refilling valve, connecting the discharge end of each feederunit to a common receiving container, refilling the storage hopper ofeach feeder unit with a powder intermittently 40 to 80 times per hour,storing data about the powder filled in the feeder unit duringrefilling, transporting powder from the storage hopper of each feederunit with the respective conveyer, and discharging powder from eachfeeder unit into the common receiving container. During each refillingof the storage hopper of each feeder unit, the respective refillingvalve dispenses approximately the same amount of the powder into thestorage hopper and during the step of transporting the powder from thestorage hopper of each feeder unit, the conveyer is operated accordingto the data collected during previous refills.

In accordance with another mode, the storage hopper is refilled 50 to 70times per hour.

In accordance with a further mode, a stabilizing time of the feedermodule is defined and the stabilizing time after each refill is in therange of 2 to 4 seconds.

In accordance with an added mode, the storage hopper of each feeder unitis provided with a predefined volume to define a capacity of below 10liters.

In accordance with an additional mode, the maximum volume of powder inthe storage hopper in each feeder unit lies in the range of 1.6 to 2liters.

In accordance with yet another mode, the powder is transported from thestorage hopper of each feeder unit to the receiving container at apredefined maximum flow rate of below 100 liters per hour.

In accordance with yet a further mode, a maximum refilling interval in his defined by a ratio of a volume of the storage hopper and a maximumflow rate.

In accordance with yet an added mode, each feeder unit is provided witha dead weight in a range of 1 to 8 kg.

In accordance with yet an additional mode, a working space in kgh isdefined by an arithmetic product of the dead weight in kg of each feederunit and the refilling interval in h and the working space is below 0.2kgh. In an exemplary embodiment, the working space is below 0.1 kgh.

In accordance with again another mode, the receiving container isconnected to a granulator and further comprising the step of granulatingthe mixture of the one or more powders to provide a granulated mixture.

In accordance with again a further mode, the receiving container isconnected to a tablet press and further comprising the step oftabletting the mixture of the one or more powders or granulated mixtureto provide a tableted pharmaceutical product.

With the objects in view, there is also provided a feeder module for usein the method, the feeder module comprising a plurality of feeder units,each feeder unit including a storage hopper, a weighing cell, aconveyer, and a discharge end, a refilling system including a refillingvalve and at least one of a level or weight indicator disposed above therefilling valve, the refilling system being connected to the storagehopper of each feeder unit, a common receiving container connected tothe discharge end of each feeder unit, and the plurality of feeder unitsare two to eight feeder units disposed in a spokes-like configuration,each feeder unit extending radially outwards from an imaginary innercircle defined by the discharge ends of the feeder units in the commonreceiving container to an imaginary outer circle defined by radiallyopposite ends of the feeder units, the feeder units being positionedsubstantially on radii extending from the imaginary inner circle.

In accordance with again an added mode, there is provided a controllerprogrammed to store a conveying parameter together with at least one ofa level or a weight.

In accordance with still another mode, the weighing cell of each feederunit is a weighing cell with Electro Magnetic Force Restoration (EMFR).

In accordance with still a further mode, the storage hopper, theconveyer, and the discharge end of each feeder unit are releasablyconnected to the weighing cell.

In accordance with still an added mode, at least one of the conveyers ofthe feeder units are twin screw conveyors.

In accordance with still an additional mode, at least one of the screwsof the twin screw conveyor has a variable pitch along its lengthunderneath the storage hopper, at least one of the screws has a variablediameter along its length underneath the storage hopper, and/or both ofthe screws have a variable diameter along its length underneath thestorage hopper.

In accordance with another mode, there is provided a controllerprogrammed to process weight signals and compensate for external forces.

In accordance with a further mode, there is provided a sensor configuredto sense material variations.

In accordance with an added mode, the storage hopper, the conveyer, andthe discharge end of the feeder unit are contained and isolated from theweighing cell.

In accordance with an additional mode, the discharge end of each feederunit is connected to the receiving container by a lay flat tube.

In accordance with yet another mode, each feeder unit has a pre-feederelement and which further comprises a lay flat tube between the storagehopper and the pre-feeder element of each feeder unit.

In accordance with again an additional mode, there is provided a casingaround the storage hopper, the conveyer and the discharge end of eachfeeder unit.

In accordance with again an added mode, a diameter of the imaginaryinner circle is smaller than a diameter of the receiving container.

In accordance with still another mode, there is provided an activevibration compensation scale integrated in the feeder module.

In accordance with a concomitant mode, the storage hopper is providedwith a stirrer device.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying figures, where like reference numerals refer toidentical or functionally similar elements throughout the separateviews, which are not true to scale, and which, together with thedetailed description below, are incorporated in and form part of thespecification, serve to illustrate further various embodiments and toexplain various principles and advantages all in accordance with thesystems, apparatuses, and methods. Advantages of embodiments of thesystems, apparatuses, and methods will be apparent from the followingdetailed description of the exemplary embodiments thereof, whichdescription should be considered in conjunction with the accompanyingdrawings in which:

FIG. 1 shows a perspective view of an embodiment of a feeder module ofthe invention;

FIG. 2 shows a top plan view of the feeder module of FIG. 1;

FIG. 2a shows a fragmentary, schematic overview corresponding to FIG. 2,in an embodiment comprising eight feeder units;

FIG. 2b shows a fragmentary, schematic overview corresponding to FIG. 2a, of another embodiment comprising seven feeder units;

FIG. 2c shows a fragmentary, schematic overview corresponding to FIG. 2a, of further embodiment comprising six feeder units;

FIG. 2d shows a fragmentary, schematic overview corresponding to FIG. 2a, of further embodiment comprising five feeder units;

FIG. 3 shows a cross-sectional view of the feeder module of FIG. 1;

FIG. 4 shows a fragmentary, detail cross-sectional view of and exemplaryembodiment of a receiving hopper or receiving container of the feedermodule of FIG. 1;

FIGS. 5 and 6 show a perspective view from above a feeder module ofanother embodiment in two different conditions;

FIG. 7 shows a partially transparent, perspective view of a detail of anembodiment of a feeder module and containment of powder contactingpowder pump;

FIGS. 8a-c show fragmentary, side views of a detail of a pre-feederelement of a feeder module;

FIG. 9a shows a vertical cross-sectional view of an embodiment of afeeder module;

FIG. 9b shows a top plan view of a feeder unit;

FIG. 9c shows a vertical cross-sectional view of a feeder module; and

FIGS. 10 and 11 show fragmentary, partially transparent plan views of adetail of two different embodiments of a feeder module.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Referring now to the Figures, a feeder module generally designated 1 isshown. In the embodiment shown, the feeder module 1 comprises aplurality of feeder units 2. Each feeder unit 2 comprises a feeder part20 and a weighing cell. A pre-feeder element 40 is attached to thefeeder part 20. In the embodiment shown in FIGS. 1 to 3, there are eightsuch feeder units 2. The feeder unit 2 according to the invention mayalso be used independently, as a single unit.

In one development of the preferred embodiment, the feeder modulecomprises five feeder units 2 and the diameter of the imaginary innercircle is 42-100 mm for a twin screw discharge tube (WDis) of 24 to 45mm and a lateral clearance (CL) in between two twin screw dischargetubes of 1 to 10 mm, see FIG. 2 d.

Alternatively, the feeder module may comprise six feeder units and thediameter of the imaginary inner circle is 50-120 mm for a twin screwdischarge tube of 24 to 45 mm and a lateral clearance (CL) in betweentwo twin screw discharge tubes of 1 to 10 mm. See FIG. 2 c.

The feeder module comprises seven feeder units and the diameter of theimaginary inner circle is 57-140 mm for a twin screw discharge tube of24 to 45 mm and a lateral clearance (CL) in between two twin screwdischarge tubes of 1 to 10 mm, see FIG. 2 b.

As a further and preferred development, the feeder module compriseseight feeder units and the diameter of the imaginary inner circle is65-150 mm for a twin screw discharge tube of 24 to 45 mm and a lateralclearance in between two twin screw discharge tubes of 1 to 10 mm, seeFIG. 2 a.

With particular reference to FIGS. 3 and 4, each feeder unit 2 includesa storage hopper 21 to contain material to be processed, a conveyer 22,a discharge end 23, and a weighing cell 24. The conveyer 22 has thefunction of transporting the material from the storage hopper 21 todischarge the material into a receiving container in a manner to bedescribed in further detail below. Furthermore, it emerges from theseFigures that the feeder units 2 are arranged in a single level todischarge into a common receiving container 3.

In the embodiment shown in FIGS. 1 to 4, the feeder units 2 aredistributed substantially evenly over 360° in the same level, i.e. onsubstantially the same horizontal plane. Thus, the feeder units 2 arearranged in a spokes-like configuration, each feeder unit 2 extendingradially outwards from an imaginary inner circle 31 defined at thedischarge end 23 facing the common receiving container 3 to an imaginaryouter circle defined by radially opposite end of each feeder unit. Thefeeder units 2 are positioned substantially on radii extending from theimaginary inner circle.

The smallest possible dimension of the imaginary inner circle 31, andhence of the receiving container 3, depends on the number of feederunits 2 and of the physical dimensions of the individual feeder units 2.Typical values in embodiments comprising five feeder units, possiblydistributed substantially evenly, are a diameter of the imaginary innercircle of 42-100 mm. In an embodiment comprising six feeder units,possibly distributed substantially evenly, the diameter of the imaginaryinner circle is typically 50-120 mm. 7 feeders 57-140 mm. In theembodiment shown in FIGS. 1 to 4, where eight feeder units 2 are adaptedto be distributed substantially evenly, the diameter of the imaginaryinner circle is typically 65 to 150 mm, in the specific embodimentapproximately 107 mm. These values are dependent also on the desiredclearance of 1-10 mm between parts of neighboring feeder units and thedimensions of the individual parts. In the embodiment shown, theapproximate width 26 of the discharge tube of each feeder unit 2 is 40mm.

The dimensioning of the feeder units 2 of the feeder module 1 depends onthe field of application. Sizing may for instance be available as arange, such that each feeder unit 2 in a module 1 is of a differentsize. In the embodiment shown and described, the dead weight of eachfeeder unit 2 is below 5 kg, and the capacity of the storage hopper ofeach feeder unit is less than 2 liters.

Correspondingly, the net weight of the powder to be filled into thestorage hop-per 21 of the individual feeder units 2 depend on the volumebut also on the kind of pow-der applied. Typically, the maximum volumeof powder in the storage hopper lies in the interval 1.6 to 2 liters.The maximum mass flow rate is approximately 50 kg/h.

The ratio of powder weight and the maximum mass flow provide a maximumrun time to empty a feeder or a maximum refilling interval pr. hour.Preferably, the arithmetic product of the maximum refilling interval [h]and the dead weight [kg] of each feeder unit 2 is below 0.1 kgh. If thepowder density is taken out of the equation and replaced by volume themaximum refilling interval is also the ratio of the hopper volume [L]and the feed rate [L/h]. E.g the capacity of the storage hopper of eachfeeder unit is less than 1.6 liters. The maximum flow rate is 100 L/h.The maximum refill interval is then 0.016 h. The dead weight of eachfeeder unit 2 is typically 5 kg.

In the embodiment described, the arithmetic product of the dead weight 5kg and the maximum refill interval 0.016 h is 0.08 kgh. The arithmeticproduct is typically below 0.2, preferably below 0.1, most preferablybelow 0.05 kgh.

Cleaning of at least some parts of the feeder module is advantageouslycarried out on a regular basis. In order to allow cleaning of inparticular the parts in contact with the powder to be processed, thestorage hopper, the conveyer and the discharge end of each feeder unitare releasably connected to the weighing cell.

FIG. 4 shows a detail cross section of the receiving hopper or receivingcontainer 3. The discharge tube end 23 of the feeder units 2 with theimaginary circle 31 is smaller than the diameter of the receivingcontainer 3. The discharged powder falls straight into the throat of thereceiving container 3 and is substantially not sticking to the innerwalls of the receiving container 3.

In the embodiment of FIGS. 5 and 6, the configuration of the feederunits 2 of the feeder module is slightly different from that of FIGS. 1to 4. Here, there are also eight feeder units 2, but they aredistributed over only a part of the circle circumscribing the dischargeends 23 and the receiving container, viz. approximately 270°. Detachmentof one feeder unit 2, for instance for cleaning purposes, is carried outby detaching the feeder unit 2 from the receiving container 3. This maytake place in a contained manner, for instance by other tightening orsealing devices, such as by Layflat tubing (LFT).

Following detachment of one feeder unit 2, the engagement of the storagehopper, the conveyer and the discharge end 23 with the weighing cell 24is released to attain the position shown in FIG. 7.

Relative to some prior art devices, it is noted that there is no bellowbetween the discharge end 23 and the receiving container. Such a bellowhas shown to influence the weighing signal due to its stiffness. Acasing 250 is provided around the storage hopper, the conveyer 22 andthe discharge end 23 of each feeder. The openings in the casing 250 aredetached from the weighing cell. The receiving container, which is alsodetached from the weighing cell, and the feeder part 20 are isolated ina contained way by means of a lay flat tube 260. Lay flat tubes 260 arepreferably made of a lightweight material having a very low stiffness,such that the weighing signal is left almost completely unaffected. Alay flat tube 260 may also be provided between the storage hopper 21 anda pre-feeder element (see FIG. 1).

Refilling of the storage hoppers of the feeding units 2 may take placeat different points in time, if expedient according to a predefinedschedule. The refilling takes place by means of a valve with aircompensation, cf. FIGS. 8a-c and part 230 in FIG. 3. Suitable valves arerepresented by plug valves, rotary dosing valves 41, butterfly valves 42and slide valves 43. Above the valve a level sensor 44 is provided foruse when the weight is fluctuating during refill of the feeder unit 2.The refilling takes place in a contained manner so as to at least assurethat no dust enters the surrounding environment by the use of anappropriate seal or tube.

During refilling, special precautions may be taken, such as for instancethe use of an algorithm to control dosing during the short refillingtime where weighing is paused, this is to compensate for the compactingeffect that arises during filling. In the algorithm, a weight issimulated to predict the correct feed factor, and once the seal isreleased, the weight of the powder in the storage hopper is corrected.Particular details of the refilling procedure will be described infurther detail below.

Referring in particular to FIGS. 9a-c , the storage hopper 21 may besupplemented by a stirrer device 211 to break any bridges formed in thepowder and to ensure that the conveyer 22 is fed properly. The conveyer22 is in the embodiment shown a twin screw conveyor. Compared to FIG. 9a, the feeder unit 2 is additionally provided with lay flat tubing 260and the receiving opening of the storage hopper 21 and at the dischargeend 23.

In the embodiment shown in FIG. 10, both of the concave screws 221 and222 of the twin screw conveyor 22 have a variable pitch along itslength, a first pitch p1 and a second pitch p2, being different from thefirst pitch P1. The conveyer 22 is driven by a motor M. In thisembodiment the diameter of each screw is constant. In the embodiment ofFIG. 11, the pitch of each screw is constant, whereas the diameter ofthe screws is variable along the length shown as diameter d1 anddiameter d2. It is also possible to have one or more screws with both avariable pitch and a variable diameter.

For both FIGS. 10 and 11 the material to be conveyed moved in thedirection of the arrow away from the motor M and into the imaginarycircle 31.

Furthermore, although not shown in the drawings, the feeder module maycomprise a number of additional features, such as analysis and controlsystems, loading and discharging stations etc.

As the feeder unit of the feeder module according to the invention has astorage hopper of a limited volume, a rapid or high frequency refillingsystem is provided.

Typically, feeders of a larger volume are refilled 4 to 8 times perhour. During refilling, the powder which is dropping into the storagehopper causes disturbances on the weight signal (due to the impactforces of the powder) over a period which is equal to the sum of thepowder drop time and scale stabilization time. Together with the time ofrolling average filters this usually takes 30 s up to 60 s to get astable weighing signal after a refill or top-up. During this time thefeeder is running in a volumetric mode. The screw speed is defined bythe Feed Factor curve, the feed factor being defined as the equivalentof the weight per screw revolution, and the accuracy depending on howgood the curve is fitting to the reality.

Typical values of the refilling frequency of the feeder module accordingto the invention are one time per minute at a feed rate of 50 kg/h, i.e.mass flow 5 kg/h refill after 10 min. Due to its reduced weight anddynamic properties, the feeder module stabilizes in 2 to 4 seconds at afeed rate of 50 kg/h.

In general, the summarized refill time of both systems is similar, butthe accuracy on the mass flow during refilling volumetric mode (RMSerror) is much better compared to conventional top-up systems.

The principle underlying the refilling system of the feeder moduleaccording to the invention is different from others as it is based onrefilling each time the same amount of power under the same conditions.The refill system has either a weighing scale or a level sensorintegrated combined with a volumetric dosing valve. The system itselfacts as a (pre)feeder and stores the number of impeller turns togetherwith a level or a weight.

Such a refill or top-up system can also be used for materialdetermination using the feeder data. Furthermore, it can be set to sensematerial variations. As the powder dosing valve always discharges in thecenter of the top-up tube, the shape of the powder stack is constant inthe same area. During the powder drop, the powder at the bottom of thehopper is more compacted than the powder at the top of the hopper.However, the powder volume in the discharge tube is still not compacted.The screw speed remains unchanged until the fresh (i.e. more compacted)material is coming to the discharge opening. Each refill is reproducibleand the system learns and converges to the optimal speed of the screws.Furthermore, analysis of feeder data with fast Fourier Transform (FFT)may be applied to determine the material and differentiate betweendifferent types of material (eg. batch to batch variation). Eventually,the feeder data may be used to calculate theoretical compositions andconfirm BU and Assay over specified time periods.

During operation, the feeder module is subjected to a number of externaland internal disturbances. The disturbances normally include mechanicalvibrations, wind load, bellow deformation forces etc. falling into oneof two main types, viz. deterministic disturbances, which can befiltered, and non-deterministic disturbances, the effect of which mustbe reduced in other ways. In order to reduce the external cyclicdisturbances, an Active Vibration Compensation (AVC) scale is integratedin the feeder module and compensates in real time the weighing signal.This improves the accuracy on the mass flow even further. In order toreduce the effect of the internal cyclic disturbances, due to gears,agitator in hopper etc., special algorithms are used for real time noisecancelling, according to the “anti-sound” principle, to dampen noisefrom screws, gearbox etc. without time delay.

Due to the low dead weight of the feeder unit, and the small hoppervolume thus limiting the weight of the powder present in the hopper, andthe dynamic EMFR weighing scale, the feeder module according to theinvention is dynamically more precise and faster responding compared toothers. For instance, the recovery from non-cyclic external disturbanceswill only take about 2 to 4 seconds.

As further features, in order to increase the accuracy even further, acontroller adapted to store a conveying parameter together with a levelor a weight may be provided, and the feeder unit may further comprise asensor for sensing material variations.

Operation of the feeding unit may take place by the method according tothe invention to be described in the following:

The method is intended for discharging a constant mass flow of one ormore powders into a receiving container. Primarily, the method formspart of a process for processing pharmaceutical products, but may alsobe applied in other fields. The method is suitable for being operated ina feeder unit 2 as described in the above and comprises the steps of:

providing a feeder unit 2 with a storage hopper 21, a weighing cell 24,a convey-er 22, and a discharge end 23,

connecting the storage hopper 21 to a refilling system with a refillingvalve 41, 42, 43,

connecting the refilling valve to a level or weight indicator 44, thelevel or weight indicator 44 being above the refilling valve 41, 42, 43,

connecting the discharge end 23 to a receiving container 3,

refilling the storage hopper 21 intermittently at predefined intervals,

storing data during refilling,

wherein during refilling, the refilling valve 41, 42, 43 dispenses thesame amount of powder into the storage hopper 21, and

the conveyer 22 is operated according to the data collected duringprevious re-fills.

Typically, the storage hopper 21 is refilled 40 to 80 times per hour,preferably 50 to 70 times per hour. The stabilizing time after eachrefill is in the range 2 to 4 seconds.

A working space is defined by the value resulting from the formula: Thearithmetic product of the dead weight [kg] of each feeder unit and therefilling interval [h] is below 0.2 or even below 0.1. Due to the lowpowder mass in the hopper a very sensitive scale can be used which leadsto a very high accuracy. The low powder mass makes a more frequentrefilling necessary.

Other aspects of the configuration of the feeder module are the subjectof Applicant's co-pending application filed on the same day as thepriority application of the present application, which co-pendingapplication was assigned International Application No. PCT/IB2012/052804and was published under International Publication WO 2013/182870 A1, andthe contents of which are incorporated by reference.

According to need (i.e. an indication of a storage hopper being empty)or as a result of a pre-programmed schedule, the storage hoppers of therespective feeder units are refilled intermittently as described in theabove.

In order to clean the parts of the feeder module in contact with thepowder(s), the method may include the further steps of detaching thestorage hopper, the conveyer and the discharge end of each feeder unitfrom the weighing cell, and cleaning the storage hopper, the conveyerand the discharge end of each feeder unit in a contained manner.

The invention should not be regarded as being limited to the embodimentsshown and described in the above. Several modifications and combinationsare conceivable within the scope of the appended claims.

What is claimed is:
 1. A feeder module, comprising: a plurality offeeder units arranged in a spokes-like configuration in a single level,the plurality of feeder units being two to eight in number, each feederunit comprising a storage hopper, a weighing cell, a conveyer, and adischarge end; and a common receiving container connected to thedischarge end of each feeder unit, each feeder unit extending radiallyoutwards from an imaginary inner circle defined by the discharge ends ofthe plurality of feeder units in the common receiving container to animaginary outer circle defined by radially opposite ends of theplurality of feeder units, the plurality of feeder units beingpositioned substantially on radii extending from the imaginary innercircle, wherein: one or more conveyers of the plurality of feeder unitsis a twin screw conveyor, at least one of the screws of the twin screwconveyor has: a length underneath the storage hopper; and at least oneof: a variable pitch along the length underneath the storage hopper; anda variable diameter along the length underneath the storage hopper. 2.The feeder module according to claim 1, wherein the plurality of feederunits are five to eight in number.
 3. The feeder module according toclaim 1, wherein each feeder unit further comprises: a refilling systemincluding a refilling valve; and at least one of a level indicator and aweight indicator located above the refilling valve, the refilling systembeing connected to the storage hopper of each of the plurality of feederunits.
 4. The feeder module according to claim 1, wherein the storagehopper, the conveyer, and the discharge end of each of the plurality offeeder units are releasably connected to the weighing cell.
 5. Thefeeder module according to claim 1, wherein the at least one of thescrews of the twin screw conveyor has the variable pitch along thelength underneath the storage hopper.
 6. The feeder module according toclaim 1, wherein the at least one of the screws of the twin screwconveyor has the variable diameter along the length underneath thestorage hopper.
 7. The feeder module according to claim 1, wherein theat least one of the screws of the twin screw conveyor has: the variablepitch along the length underneath the storage hopper; and the variablediameter along the length underneath the storage hopper.
 8. The feedermodule according to claim 1, further comprising a controller configuredto process weight signals and to compensate external forces.
 9. Thefeeder module according to claim 1, further comprising a sensorconfigured to sense material variations.
 10. The feeder module accordingto claim 1, wherein the storage hopper, the conveyer, and the dischargeend of the feeder unit are contained and isolated from the weighingcell.
 11. The feeder module according to claim 1, further comprising atleast one lay flat tube, the discharge end of each of the plurality offeeder units being connected to the common receiving container by thelay flat tube.
 12. The feeder module according to claim 11, wherein:each of the plurality of feeder units comprises a pre-feeder element;and the lay flat tube is a plurality of lay flat tubes each between thestorage hopper and the pre-feeder element of a respective one of theplurality of feeder units.
 13. The feeder module according to claim 12,further comprising a casing disposed around the storage hopper, theconveyer, and the discharge end of each of the plurality of feederunits.
 14. The feeder module according to claim 1, wherein: the commonreceiving container has a diameter; and the diameter of the imaginaryinner circle is smaller than the diameter of the common receivingcontainer.
 15. The feeder module according to claim 1, furthercomprising an integrated active vibration compensation scale.
 16. Thefeeder module according to claim 1, wherein the storage hopper comprisesa stirrer device.
 17. The feeder module according to claim 1, wherein asmallest possible dimension of the imaginary inner circle and,therefore, of the common receiving container, is dependent upon a numberof the plurality of feeder units and upon physical dimensions ofindividual ones of the plurality of feeder units.
 18. The feeder moduleaccording to claim 17, wherein: the number of the plurality of feederunits is five feeder units distributed substantially evenly about theimaginary inner circle; and a diameter of the imaginary inner circle isbetween approximately 42 mm and approximately 100 mm.
 19. The feedermodule according to claim 1, wherein: the number of the plurality offeeder units is six feeder units distributed substantially evenly aboutthe imaginary inner circle; and a diameter of the imaginary inner circleis between approximately 50 mm and approximately 120 mm.
 20. The feedermodule according to claim 1, wherein: the number of the plurality offeeder units is seven feeder units distributed substantially evenlyabout the imaginary inner circle; and a diameter of the imaginary innercircle is between approximately 57 and approximately 140 mm.
 21. Thefeeder module according to claim 1, wherein: the number of the pluralityof feeder units is eight feeder units distributed substantially evenlyabout the imaginary inner circle; and a diameter of the imaginary innercircle is between approximately 65 mm and approximately 150 mm.
 22. Thefeeder module according to claim 21, wherein the diameter of theimaginary inner circle is approximately 107 mm.
 23. The feeder moduleaccording to claim 1, wherein a lateral clearance between parts ofneighbouring feeder units is between approximately 1 mm andapproximately 10 mm.
 24. The feeder module according to claim 23,wherein: one or more conveyers of the plurality of feeder units is atwin screw conveyor; the feeder units associated with the one or moreconveyers have twin screw discharge tubes; and the lateral clearance inbetween two of the twin screw discharge tubes is between approximately 1mm to approximately 10 mm.
 25. The feeder module according to claim 24,wherein: the common receiving container has a diameter; and a dischargetube end of the plurality of feeder units with the imaginary innercircle is smaller than the diameter of the receiving container.
 26. Amethod for providing a mixture of one or more powders in a commonreceiving container using the feeder module of claim 1, which comprises:providing each of a plurality of feeder units with a storage hopper, aweighing cell, a conveyer, and a discharge end; providing a commonreceiving container; configuring the plurality of feeder units with therespective discharge ends facing the common receiving container in asingle level; connecting the discharge end of the plurality of feederunits to the common receiving container; refilling the storage hopper ofa respective one of the plurality of feeder units with a powder; andfeeding the powder from the respective storage hopper to the commonreceiving container to provide the mixture.
 27. The method according toclaim 26, wherein the common receiving container has inner walls and athroat and, which further comprises, allowing the discharged powder tofall straight into the throat of the receiving container and therebysubstantially prevent the falling powder to stick to the inner walls ofthe common receiving container.